Control system



Aug. 18, 1931. H. D. JAMES 1,819,465.

. CONTROL SYSTEM Filed Feb. 17, 1928 Hency BY a James.

Patented Aug. 18, 1931' PATENT OFFICE UNITED STATES- KENRY D. 31m, OE BWIBSVALE, IENNSYLVANLA, ASSIGNOR T O WESTINGHOUSE ELECTRIC & HANUFACTURING COM}. ANY, A CORPORATION 01' PENNSYLVANIA CONTB'OL SYSTEM.

Applicatlomfled February 17,1928. Serial 17o. 255,048.

The invention relates generally to systems of controland moreparticularly to the system of control for motors employed in operating hoisting apparatus.

' The object of the invention, generally stated, is to provide for controlling the lowering speed of electric motors employed in operating hoists or apparatus having similar c a racteristics. A more specific object of the invention is to provide for lowering the hoist at relatively high speeds when the hoist is unloaded or carrying a light load and to automatically prevent it from exceedin a safe lowering speed when heavily loader i.

Afurther-object of the invention-is to provide for maintaining an electromagnetic brake energized and released at all times when the motor is being operated to either raise or lower the hoist.

For a better understanding of the invention, reference may be had to the following description taken in conjunction with the accompanyin drawing, wherein: The figure 1s a schematic illustration of control system arranged in accordance with my invention.

In the drawing,

anelectric motor 1 of the direct current series type is shown provided with a field windin 2 and an armature 3 which may be suitab y coupled to the operating mechanism of a hoist. Since the construction of hoists. and the manner of in- 3 stalling motors for operating them is well known it is not deemed necessary to illustrate t e same. 7 7

A drum controller 4 having a plurality of contact segments is providedfor controlling the operation of the motor 1. The contact segment 5 of the drum controller4 is disposed to engage the contact finger a which in turn is connected to line conductor L1. Contact segment 6 engages contact finger b to complete an energizing circuit for the actuating coil 21:: of the electromagnetic line contactor 21. Contact segment 7 engages contact finger cfor completing the energizmg 23a, of the other line contactors 22 and 23,

circuit f01fth0 actuating coils 22a and.

which circuits, when completed, efiect the closing of the contactors 21, 22 and 23.

Therefore, when the drum controller 4 is moved in the indicated direction raise to position 1, contactors 21, 22 and 23 are closed and establish a power circuit for the motor 1 which may be traced from line conductor L2 through contactors 22 and 21, the armature 3, series field winding 2, a resistor 32, I the, electromagnetic brake coil 43a, resistor 34, contactor 23 to line conductor L1. The motor is caused to operate in the proper direction for raising the hoist.

Resistors 32 and 34 are provided for preventing 'excesiv'e startin currents in the motor and also -for-mak1ng it possible to operate the motor at different speeds. In order to short circuit the sections 28, 29 and 31 of the resistor 34 and the resistor 32, the electromagnetic contactors 24, 25, 26 and 27, respectively, are employed. When the drum controller 4 is moved through the different indicated raise positions 2, 3, 4 and 5, contact fingers d, 0,] and g on the controller enga e the contact segments 8, 9, 10 and 11in t e order named, completing the energizing circuits for the actuating coils 24a, 25, 26a and 27a, respectively, c osing the accelerating contactors 24, 25, 26 and 27, which contactors in closing, short circuit the 80 respective sections 28, 29 and 31 of the current limiting resistor 34 and also the resistor It will be readily seen that if it is desired to 0 rate the motor at a predetermined spee the drum controller may be disposed in one of the difierent ositions 1, 2, 3, 4 and 5, thereby allowing di erent portions of the resistors to remain in the motor circuit.

When it is desired to lower the hoist, the motor is reversed by moving, the drum controller 4 in the direction indicated lower and when in the. first position, the contact segments 12, 13, 14, 15, 16, 17 and 18 of the drum switch engage the contact fingers 0:, c d, e, f, g and h, res ctively, completi t e energizing circuits or the actuatin co$ 22a, 23a, 24a, 25a, 26a, 27a, 36a an 37a, closin the contactors 22 23, 24, 25, 26, 27, 36 an 37 respectively. The closing of con- 10c position isclosed, the brake coil 43a, contactors 26, 25, 24 and 23 to line conductor L1. Upon the closing of contactor 37, a

' ting it to run at hi her speeds.

. coils 44a,

of connecting the resistor 49 6 finger a",

power circuit for the armature of the motor is also established and the direction of flow of current through the armature is reversed and may be traced as flowing from line conductor L2 through contactors 22 and 36, resistor 38, armature 3, relay coil 39, dynamic braking resistor 42, contactors 37 and 23 to line conductor L1. When the motor is connected in this manner, it is connected to operate as a shunt wound motor. Since the resistors 32 and 34 are short-circuited, the greatest amount of field strength is provided for starting the motor in the lowering direction. In order to increase the lowering speed of the motor, the resistors 32 and 34 may be inserted in series circuit relation with the series field winding 2 by actuating the drum switch through the positions 2, 3, 4 and 5 as indicated, deenergizing the actuating coils 24a, 25a, tactors 24, 25, 26 and 27, respectively, and allowing them to fall open, as the contact segments 14, 15, 16, and 17 pass out of engagement with the contact fingers d, e, f and g. The-resistors 32 and 34 so inserted re duce the magnetic field of the motor rmit- Whidn the drum controller 4 1s movedto position 5 lower, contact segment 19 comes into engagement with contact member 71, completing an energizing circuit for the actuating 45a, 46a, 47a of contactors 44, 45, 46, and 47, respectively, which contactors are provided for controlling the amount of the resistor 49 connected in shunt circuit relation to theseries field windin 2 and resistor 32. The resistor 49 is provi ed for further controlling the lowering speed of the motor, and is connected in shunt relation to the series field winding 2 for also reducing the field strength of the motor. The purpose across the resistor 32,- as well as the field winding 2 is because the resistance value of the field winding is so low that if the resistor 49 were connected in shunt relation to the field winding alone, the varying contact resistance of the contactors 45, 46 and 47 would greatly afiect the operation'of the system.

The energizing circuit for the actuating coils of the contactors 44, 45, 46 and 47 e2:- tends-from line conductor L1 through contact segments 12 to 19 inclusive, contact back contact members or interlocks resistor 38 which is provided for 26a and 27a of the con 51 52 53 and 54,, of the respective current limit relays 51, 52, 53 and 54 and the actuating coils 44a, 45a, 46a and 47a, respectively, whichcoils are connected in parallel circuit relation, to conductors L1 and L2. The closin of contactor 44 completes a circuit extending from one side of the'series field winding 2 through contactor 44, re sistor 49, resistor 32 to the other side of the series field winding. When contactor 44 is initially closed, contactors 45, 46 and 47 are also closed, and, sections 56, 57 and 58 of the resistor 49 are short-circuited.

In order to control the operation of the contactors 44, 45, 46 and 47 automatically, so that the speed of the motor will be prevented automatically from exceeding a safe lowering speed when the hoist is heavily loaded, the current relays 51, 52, 53 and 54 are provided, upon which are mounted interlocks 51?), 52b, 53b and 54b which complete the circuits for the actuating coils 44a, 45a, 46a and 47a when the current rela s are deenergized, which occurs whenever t e mature 3 of the motor and a coil 39 is con nected in series circuit relation with the armature'3. The coils are disposed to so affect each other differentially that the relay shall remain closed when the motor is operatin as a motor, but upon the reversal of the direction of flow of current through the series coil 39 when the motor is being driven as a generator, the relay is actuated to its circuit interrupting position and, inasmuch as it is connected in circuit relation with the actuating coil 22 of the contactor 22, line contactor 22 falls open, disconnectin the motor from the power supply.

'TVhen contactor 22 opens, interlock 226 com letes a circuit extendin from one side of t e armature 3 through't e series coil 39 of the relay 41, interlock 226, the actuating coil 51a of relay 51 to the other side of the armature 3. The relay 51 may be constructed to respond to predetermined current conditions. Consequently, when the motor is driven as a generator by the lowering load and reaches a predetermined speed, or generates a predetermined voltage the relay 51 is actuated. When actuated, the interlock 51b interrufpts the circuit for the actuating coil 45a 0 contactor 45, permitting the contactor 45 to fall open, inserting section 56 of resistor 49 in shunt relation with the series field winding 2, which causes more current to flow through the series field winding, increasing the magnetic field of the motor, which tends to the of the motor or, in other words, dynamically brake t e same.

When relay 51 is. closed, contact member manner as contactor 45 and if the load still continues to drive the motor as a generator with increasing speed, the rela s 53 and '54 will close in sequence, until 1: e entire resister 49 is in shunt relation with the series field winding, thus progressively increasing m the field strength of the seriesfield winding 2, causing the motor to be operated as a generator at full field, which automaticall prevents the hoist from running away wit the motor when loaded within the capacity of the hoist.

When the motor is running in either direction; if the drum controller 4 is moved to the ofi position, interlock 23b on contactor 23 establishes a d amic braking circuit for the motor whic extends from one side of the'armature 3 through the coil 39 of the relay 4i, dynamic brakin resistor 42, interlock 23?), series field win ing 2 to the other side of the armature. The ohmic resistance oi the d amic braking resistor 42 may be of a very ow value, in order that the motor shall develo a-high dynamic-braking efiort. It will he 'oserved that in this system the electromagnetic brake coil 43a is connected 49 in such a manner that it will be energized whenever the drum controller is disposed in an operating) position, accordingly -maintaining the rake 43 inoperative w enever the hoist is being raised or lowered. It will also be noted that when the motor is connected to operate as a shunt wound motor to lower the hoist, and is caused to rate as a generator, circuits will be estab ished automatically to efiect operation of the motor as a series wound nerator.

Since the relay 41, w en open, operates to disconnect the motor from the source of supply and to connect the motor for operation as a series-wound generator, heavy loads ma be lowered with safety and at permissib e speeds.

While the illustrated example constitutes a preferred embodiment of the invention, it is not desired to limit the invention strictly to the details shown, since the embodimentdescribed may be considerably varied without departing fromv the spirit of the invention as defined in the'appended claims.

I'claim as my invention:

c5 1. In a control system, in combination, a

dynamo electric machine provided with an armature and a field winding, means for connecting the armature and eld winding in series circuit relation for operation in one direction and for connecting the armature windin and field winding in parallel circuit relation for operatin the motor in the other direction, a variab e resistor connected in shunt relation to the field winding, and means responsive to the speed of the motor when running-in one direction for establishing a dynamic braking circuit and varying the variable resistor.

2. In a motor control system, in combination a direct current motor having a field winding and an armature winding, a source of current, means for connecting the armature winding and field winding in series circuit relation to the source of current for operating the motor in one direction and for connecting them in parallel circuit relation I for operation in the reverse direction, a variable field resistor, means for connecting said variable resistor in shunt circuit relation to the field winding when the field winding is connected in parallel circuit relation to the armature winding, andelectro-responsive means for varying said resistor in accordance with the voltage developed by said motor acting as a generator, 95

3. In a control system for hoist operating motors, in combination, a direct current 1110- tor, a source of energy, means for connecting the motor to the source of energy to operate as a series wound motor for raising a load and for connecting it to operate as a shunt wound motor for lowering a load, means for varying the field strength of the motor when operating as a shunt wound motor to control the speed of the motor when lowering a load, and means for automatically disconnecting the motor from the source of ener when the motor is lowering a load and the oad causes the motor to'operate as a generator and means responsive to said disconnectin means for automatically rendering the fiel varying means responsive to the speed of the motor.

4. In a control system for hoist operating motors in combination, a direct current mo- 115 tor, a eld winding and an armature winding for the motor, a current limiting resistor for the motor, a source of current, a manually operable controller, switching mechanism responsive to the manually oper- 12o able controller when operating in one direction for connecting the armature wind-- ing and the field winding and the resistor in series circuit relation to the source of current and for short circuiting the resistor, 125 other switching mechanism responsive to the controller when actuated in the reverse direction for reversing connection of the armature winding and connecting the field winding in parallel circuit relatlon to the arma- 130 ture winding, of the motor field when connected to operate as a shunt motor and means for automatically disconnecting the motor from the source of current when a heavy lowering load causes the motor to operate as a generator, said means rendering the field varying means responsive to the voltage generated by the motor to regulate the speed of the motor.

5. In a control system for hoist operation, in combination, a reversible direct current motor, a field winding, an armature winding, and a current limiting resistor for the motor, a source of current, a manually operable switch for connecting the armature winding, the field winding and the current limiting resistor in series circuit relation to the source of current when the manually operable switch is moved to connect the motor for operation in a hoist raising direction, means responsive to the manually operable switch for short circuiting the current limiting resistor, means also responsive to said switch when operated in the reverse direction for reversing the directions of current to the armature and for connecting the field winding and the current limiting resistor in series circuit relation to the source of current and in parallel circuit relation to the armature winding for lowering a load, means automatically responsive to the change in direction of current in the armature winding for disconnecting the motor from the source of current when a lowering load causes the motor to operate as a generator and for establishing a circuit for dynamically braking the motor when so operated, a variable resistor for changing the field strength of the motor when operating as a generator and means automatically responslve to the voltage generated by the motor for controlling regulate the lowering speed of the load.

6. In a control system for hoist operating motors, in combination, a reversible motor, a field winding, a current limiting resistor for the motor, a source of current, means for connecting the armature winding, the'field winding and the current limiting resistor in series cir-i cuit relation to the source of current to operate the motor to raise a load and means for short circuiting the current limiting resistor, means for connecting the armature winding to the source of current and means for connecting the field winding in series circuit relation with the current; limiting resistor to the source of current when opermeans for varying the strength,

the field resistor to an armature winding and .tion as a generator.

7. In a control system, in combination, a direct current motor for operating hoisting apparatus, a field winding and an armature winding for the motor, a source of current, means for connecting the motor to said source to operate as a series Wound motor when raising the hoist and to connect it to operate as a shunt wound motor when lowering thehoist, means for varying the field strength of the field winding when connected for lowering a load, and means responsive to the voltage generated by the motor when it is caused to operate as a generator by a lowering load for rendering the field varying means responsive to voltage generated to automatically prevent the motor exceeding a safe lowering speed.

8; In a control system for electrically operated hoisting apparatus, in combination, a direct current motor, means for connecting the motor to operate as a series wound motor for raising a load and for connecting it to operate as a shunt wound motor for lowering a load, current a-ndvoltage responsive means disposed to disconnect the motor from the source when a lowering load causes the motor to operate as a generator, means for establishing a circuit for efi'ecting dynamic braking when the motor circuit is mterrupted, voltage responsive means for varying the shunt field of the motor when operating as a generator, an electromagnetic brake for brakin the motor, and a circuit for energizing the rake to render it inoperative when the motor is energized.

In testimony whereof, I have hereunto subscribed my name this 10th day of February, 1928. Y

. HENRY D. JAMES.

ating the motor to lower a load, a variable I resistor for varying the current in the field winding and means for automatically varying the resistor, means for disconnecting the motor from the source of current when it is caused to operate as a generator by a lower- 

